A station blackout experiment called SBO-01 was performed at the ATLAS facility. From the SBO-01 test, the station blackout scenario can be characterized into two typical phases: A first phase characterized by decay heat removal through secondary safety valves until the SG dryouts, and a second phas...
A station blackout experiment called SBO-01 was performed at the ATLAS facility. From the SBO-01 test, the station blackout scenario can be characterized into two typical phases: A first phase characterized by decay heat removal through secondary safety valves until the SG dryouts, and a second phase characterized by an energy release through a blowdown of the primary system after the SG dryouts. During the second phase, some physical phenomena of the change over a pressurizer function, i.e., the pressurizer being full before the POSRV $1^{st}$ opening and then its function being taken by the RV, and the termination of normal natural circulation flow were identified. Finally, a core heatup occurred at a low core water level, although under a significant amount of PZR inventory, whose drainage seemed to be hindered owing to the pressurizer function by the RV. The transient of SBO-01 is well reproduced in the calculation using the MARS code.
A station blackout experiment called SBO-01 was performed at the ATLAS facility. From the SBO-01 test, the station blackout scenario can be characterized into two typical phases: A first phase characterized by decay heat removal through secondary safety valves until the SG dryouts, and a second phase characterized by an energy release through a blowdown of the primary system after the SG dryouts. During the second phase, some physical phenomena of the change over a pressurizer function, i.e., the pressurizer being full before the POSRV $1^{st}$ opening and then its function being taken by the RV, and the termination of normal natural circulation flow were identified. Finally, a core heatup occurred at a low core water level, although under a significant amount of PZR inventory, whose drainage seemed to be hindered owing to the pressurizer function by the RV. The transient of SBO-01 is well reproduced in the calculation using the MARS code.
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가설 설정
Then, after the 2nd POSRV opening of around 8300 seconds, the flow direction of HL-1 became negative again and remained for the remainder of the test, as shown in Fig. 9. Although the flow direction of the HL-1 became negative in a later period, that of the HL-2 would not be affected due to the PZR. When the POSRV is opening, the main flow from the core to the POSRV was sustained, which is why a positive flow direction was sustained in the HL-2.
제안 방법
In a real plant transient, where the SG leakage probability is low, the ATLAS model without SG leakage might be more representative of the plant transients. As the ATLAS model is validated based on a comparison of the transients between the code calculation and experiment, the validated ATLAS model can be further employed to investigate the other possible SBO scenarios since the SBO-01 scenario is just one postulated SBO sequence. In addition, the model can be used to study the scaling distortion of ATLAS in the simulation SBO by comparing the transients of the calculated SBO between ATLAS and the APR1400.
When the heat removal through the steam generators became negligible, the primary pressure started to increase until the opening setpoint of the power operated safety relief valve (POSRV). For the SBO-01 test, a total 4 POSRV openings occurred at 7,900, 8,300, 9,250, and 10,700 seconds, respectively. The accumulated leakage for the POSRV openings is also shown in Fig.
As the ATLAS model is validated based on a comparison of the transients between the code calculation and experiment, the validated ATLAS model can be further employed to investigate the other possible SBO scenarios since the SBO-01 scenario is just one postulated SBO sequence. In addition, the model can be used to study the scaling distortion of ATLAS in the simulation SBO by comparing the transients of the calculated SBO between ATLAS and the APR1400.
For a steady state calculation, a text input file, which describes the geometrical and thermal-hydraulic conditions of the nodalized volumes representing the flow path of various components in ATLAS, were made. In the experiment, the values of the most important thermal-hydraulic parameters such as the pressure, temperature, and differential pressure were measured. These measured values are then used to specify the initial thermal-hydraulic conditions of nodalized volumes in the code input file.
Under a steady state condition, the core power generated by electrical heaters was balanced with the energy removal by the secondary system. The obtained steady state condition was maintained to stabilize the system behavior of ATLAS for more than 10 minutes, and the test then began by recording the DAS data. The core heater power was initially 8% of the scaled full power and programmed to then follow a decay power table.
A best-estimate safety analysis methodology which is now commonly accepted in the nuclear community, was applied to the transient calculation of the APR1400. The pre-test calculation was conducted with the assumption that the loss of on-site and off-site powers occur simultaneously with the failure of the emergency diesel generators and the auxiliary feedwater system including turbine-driven pumps. As for the core power, a conservative 1973 ANS decay heat curve with a 1.
이론/모형
A station blackout test of ATLAS, named SBO-01, was performed according to the following experimental procedure. Essentially, the experimental conditions for the present test were determined by a pre-test calculation with a best-estimate thermal hydraulic code, MARS. Initially, a transient calculation was performed for the station blackout of the prototypic plant, APR1400, to obtain the initial reference and boundary conditions.
, start of an SBO at time zero, no diesel and AC powers, no auxiliary feedwater pumps (motor-driven and turbinedriven), etc. In this paper, an overview of the SBO test results is described including the results of analytical calculations simulating the SBO test using the MARS code [4].
The MARS code was developed by KAERI for a realistic multi-dimensional thermal-hydraulic system analysis of light water reactor transients [4]. It is based on the multidimensional code, COBRA-TF, and one-dimensional system code, RELAP5/MOD3.
성능/효과
However, some deviations between the calculation and experiment are also observed. Based on the comparison and calculated results, it was inferred that these deviations are mainly contributed to the non-existent modeling of SG leakage that exists in the experiment and a neglect of RCS heat loss in the code calculation. In a real plant transient, where the SG leakage probability is low, the ATLAS model without SG leakage might be more representative of the plant transients.
참고문헌 (13)
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K. Y. Choi et al., "Experimental Simulation of a Direct Vessel Injection Line Break of the APR1400 with the ATLAS," Nuclear Engineering and Technology, 41, 655 (2009).
K. Y. Choi, et al., "Integral Behavior of the ATLAS Facility for a 3-inch Small Break Loss of Coolant Accident," Nuclear Engineering and Technology, 40, 199 (2008).
S. Cho et al., "Core Thermal Hydraulic Behavior During the Reflood Phase of Cold-leg LBLOCA Experiments using the ATLAS Test Facility," Nuclear Engineering and Technology, 41, 1263 (2009).
H. S. Park et al., "An Integral Effect Test on the LBLOCA Reflood Phenomena for the APR1400 using the ATLAS under a Best-Estimate Condition," J. of Nuclear Science and Technology, 46, 1059 (2009).
K.Y. Choi et al., "Double-Ended Break Test of an 8.5 inch Direct Vessel Injection Line Using the ATLAS," KAERI/TR-3990/2010, Korea Atomic Energy Research Institute (2010).
Xin-Guo Yu, Hyeon-Sik Park and Ki-Yong Choi, "Post- Test Calculation of A Feedwater Line Break Test performed at ATLAS," WORTH-5, NPIC, Sichuan, China (2011).
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